This invention is directed to a chemical anchoring adhesive in the form of a self-contained, cuttable, elongated flexible rope. The rope can be cut or sheared to any desired slug length at the job site, allowing for on-site optimization of the amount of anchoring adhesive used in boreholes of varying depth and size. The cross-sectional composition is substantially uniform along the axial length of the rope.
Chemical anchoring adhesives are known which are composed of two or more components that react together and cure when mixed. U.S. Pat. No. 5,730,557, issued to Skupian et al., discloses a mortar mixture capsule unit for chemical attachment of anchors in boreholes. The capsule houses a filler material, and a chemical binder system contained in smaller capsules within the filler material. The cartridge is inserted into a borehole, and a driving tool is used to insert an anchor. The driving tool imparts motion to the anchor, which ruptures both the housing capsule and the smaller capsules contained within it, causing the chemical binder system to interact and mix with the filler. The interaction and mixing causes reaction and curing of the binder system/filler mixture, thereby securing the anchor within the borehole. A similar adhesive is sold by Hilti AG under the trade name xe2x80x9cHVUxe2x80x9d.
U.S. Pat. No. 5,731,366, issued to Moench et al., discloses a chemical plugging compound based on a free-radically polymerizable resin and a free-radical initiator spatially separated from the resin. The spatial separation can be effected by encapsulating the initiator in glass, gelatin or cellulose capsules. The plugging compound is described as being self-supporting and storage stable.
This and other prior art chemical anchoring adhesives have certain disadvantages. One disadvantage is that one or both components are fluid, and must be wrapped, encapsulated or otherwise and enclosed in a package prior to use. Thus, it is not easy to vary the amount of adhesive used in a borehole, or the size of the housing capsule, while at the job site. Put another way, oversized and undersized boreholes often receive the same amount of predetermined, pre-packaged adhesive as boreholes of standard size.
Another disadvantage is that the fluid adhesives may flow or spill from the boreholes during use, particularly after the package is ruptured by the anchor being driven. This problem is especially acute when the borehole is upside down and vertical, but also exists when the borehole is horizontal, or at an angle between horizontal and upside down vertical. Even when the adhesive is not completely fluid, the prior art cartridges are typically not self-retentive, i.e., the cartridges will fall from overhead boreholes.
Another disadvantage is that the two components, binder and filler, must be completely segregated prior to use, to prevent premature interaction and reaction. The encapsulation techniques used to accomplish this require some precision and expense. Also, there is no assurance that the smaller capsules used to contain the binder will remain evenly dispersed among the filler until the adhesive capsule is used. Uneven dispersion of the binder and filler can lead to uneven or inadequate adhesion of the anchor.
Cartridge adhesives are another type of prior art adhesive. Cartridge adhesives include two separate parts which are simultaneously injected into a borehole using a two-barrel caulking gun which brings the two parts together at the point of injection, whereupon they react upon entering the borehole. Disadvantages of cartridge adhesives include excessive packaging waste, excessive adhesive waste due to unmixed, unused material remaining in the caulking barrels, and insufficient viscosity, which permits the material to run out of vertical overhead boreholes, and to sag in horizontal boreholes.
The present invention is directed to a two-part chemical anchoring adhesive in the form of a self-contained rope. The term xe2x80x9cropexe2x80x9d refers to any elongated flexible form having a ratio of length to mean diameter of at least 10:1. The term xe2x80x9cself-containedxe2x80x9d means that the chemical anchoring adhesive is sufficiently viscous that it does not flow, and generally does not deform, unless subjected to an external force. Generally, this requires the adhesive to have a thick putty-like consistency, and a viscosity of about 5 million to about 50 million centipoise. The rope may be wrapped in a plastic film, but would be self-contained with or without a wrapper.
The two parts of the chemical anchoring adhesive are formed side-by-side, or with one part surrounding the other, so that there is an interface between them. The rope has a composition which is substantially axially homogeneous. This means that, at any axial location along the length of the rope, the compositional ratio of the first part to the second part measured through a cross-section of the rope is about the same as at any other axial location along the rope. This ensures that any slug of adhesive cut from the rope will have about the same overall composition as any other slug cut from the same rope.
The first part of the adhesive comprises a resin. The first part has a viscosity between about 5 million and about 50 million centipoise, measured at 25xc2x0 C. using a Brookfield Viscometer, Model DV-3, made by Brookfield Engineering Co. This viscosity range assures that the rope of adhesive may be formed, shaped, and/or cut with a knife, but will not flow. In one embodiment, the first part of the adhesive includes an epoxy resin (e.g., a liquid epoxy resin), and at least one particulate filler, in proportions required to achieve the desired viscosity.
The second part of the adhesive comprises a curing agent. The second part has a viscosity between about 5 million and about 50 million centipoise, measured using the same test equipment. The viscosity of the second part is not more than 30% higher or 30% lower than the viscosity of the first part. In the one embodiment, the second part of the adhesive includes a curing compound, a curing accelerator, and at least one particulate filler, in proportions required to achieve the desired viscosity.
The two parts are directly joined along an interface, without causing significant premature reaction between the two parts and without encapsulating one relative to the other. Because of their high viscosity, the two-part adhesive can be employed in an upside down vertical borehole, a horizontal borehole, or a borehole having an angle between horizontal and upside down vertical, and will not spill or flow from the borehole.
The first and second parts can be extruded, pressed, or otherwise directly joined together. The rope may have a cylindrical, rectangular, square, triangular, or other suitable shape. The rope may have any suitable cross-sectional diameter, and any suitable length provided that the length of the rope is at least 10 times its diameter. When a wrapper is used, it may be a plastic film, metal foil, paper, or the like.
The rope of anchoring adhesive may be cut or sheared to any size, depending on the depth of the borehole. The proper amount of adhesive can be measured by the depth of the borehole, i.e., by inserting a rope end into the borehole as far as possible, cutting the rope at the top of the borehole to form a slug having a length equal to the borehole depth. If the boreholes vary in depth, the adhesive may be cut or sheared to various lengths on the job site, to provide the optimum amount of adhesive slug for each borehole. Thus, the adhesive composition is both self-measuring and self-retentive due to its shape, viscosity and axial homogeneity. The rotational and/or axial motion of an anchor pin in the borehole, transmitted from a driving tool, causes mixing of the two adhesive parts in the borehole, and curing in the space between the anchor pin and wall of the borehole.
With the foregoing in mind, it is a feature and advantage of the invention to provide a rope formed of highly viscous, two-part anchoring adhesive which can be used in a downward or horizontally-opening borehole without spilling from the borehole.
It is also a feature and advantage of the invention to provide a two-part anchoring adhesive rope having a consistent composition along its axial length, which provides consistent high-quality anchoring force in heavy construction applications, and which can be cut to any desired length on the job site, or before reaching the job site.
The foregoing and other features and advantages will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings and examples. The detailed description, drawings and examples are illustrative rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof.